Given that many users utilize computing devices to perform various confidential tasks, such as banking, shopping, work-related tasks, etc., privacy when performing these tasks is a big concern. While many software solutions exist to help protect the data itself, such as encryption, access control, and so on, one large security risk still exists in the design of the computing device itself. Specifically, computing devices still almost always contain displays, which allow the user to see a virtual workspace while performing various tasks on the computing device. This display can almost as easily allow another person who is in the vicinity of the computing device to see everything the user is doing, merely by, for example, peering over the user's shoulder. This risk extends to all sorts of computing devices with displays, from ATM machines to mobile phones to laptop computers to desktop computers, and so on. All allow the user's privacy to be invaded, either intentionally or unintentionally, by other people, merely by the fact that they project light in the vicinity of the user's eyes.
One solution to this problem is to use a privacy filter. A privacy filter is a semi-transparent screen that is placed over the display of the computing device. The filter is generally composed of polycarbonate or acrylic plastic, and contains a film that acts to reduce the viewing angle of the display. As such, users viewing the display from the side cannot see the contents of the display, but a user viewing the display from straight-on can. This effectively eliminates the ability of most other people in the vicinity of the user from invading the user's privacy by viewing what is on the display.
FIG. 1 is a diagram illustrating the operation of a privacy filter screen. The screen 100 contains non-transparent slits 102a, 102b, that act as a fence. While a user who is sitting directly in front of the display can see portions 104a, 104b of the display that are behind the non-transparent slits 102a, 102b by virtue of his or her eye location 106a, 106b, users attempting to view the display from a different angle will be blocked from these area behind the slits 102a, 102b by virtue of their steeper angle of viewing.
While these types of privacy screens can be effective for many purposes, they suffer from several drawbacks. First of all, they must be physically installed on the display. Some users would actually prefer that no such privacy filter be installed (for example, if they like to have their family be able to view the display at the same time as themselves), while other users prefer that the privacy filter be installed. As such, it is difficult for a manufacturer to build such screens into the hardware of the device as some users will object to its presence. This has caused the displays to largely be an aftermarket device, installed by a user after purchase of the device, which can be burdensome on the user. Additionally, once installed, the privacy screens operate all the time until they are removed. But there may be users who wish to use the privacy screens for some of the time (when doing work, for example) while not the rest of the time (when watching movies, for example), and it is not really feasible for the user to remove the filter and put it back on when transitioning between these types of tasks.